MEC 596: Projects in Mechanical
Engineering
Wastewater Treatment CIDI Power Plant Analysis
By: Teddy Hafif
Academic Advisor: Dimitris Assanis
Additional Credit: James Gowans, Joe Koch, Simon Lin, and Jon Arneth
1
Table of Contents
Chapter 1:................................................................................................................................................................................ 3
Background: ........................................................................................................................................................................ 3
Power Production: .............................................................................................................................................................. 3
Project Goals: ...................................................................................................................................................................... 4
Chapter 2:................................................................................................................................................................................ 4
Engine:................................................................................................................................................................................. 4
Engine Data: ........................................................................................................................................................................ 5
Chapter 3:................................................................................................................................................................................ 6
Fuel Properties: ................................................................................................................................................................... 6
Usage per Cycle: .................................................................................................................................................................. 7
Air: ................................................................................................................................................................................... 7
Natural Gas: .................................................................................................................................................................... 7
Diesel:.............................................................................................................................................................................. 8
A/F Ratio: ............................................................................................................................................................................ 9
Power cycle and Engine Parameters: ................................................................................................................................ 10
Constant Pressure Cycle:............................................................................................................................................... 10
Instantaneous Volume: ................................................................................................................................................. 11
Natural Gas: .................................................................................................................................................................. 12
NG-DSL: ......................................................................................................................................................................... 14
DSL: ............................................................................................................................................................................... 17
Power Produced:............................................................................................................................................................... 19
Chapter 4:.............................................................................................................................................................................. 19
Chemical Balance: ............................................................................................................................................................. 19
Balance of methane: ..................................................................................................................................................... 20
GREET Analysis: ................................................................................................................................................................. 21
Natural Gas: ...................................................................................................................................................................... 21
Diesel:................................................................................................................................................................................ 22
Emission Comparison: ....................................................................................................................................................... 23
Chapter 5:.............................................................................................................................................................................. 24
Conclusion: ........................................................................................................................................................................ 24
Terminology: ......................................................................................................................................................................... 25
References: ........................................................................................................................................................................... 25
2
Chapter 1:
In this chapter, we will be outlying the project details to lay a foundation for the coming task.
Additionally, presenting the method of power production for the Cedar Creek facility. We will then set a goal
for what the remainder of this project will accomplish.
Background:
When most people turn on their faucet, take a shower, or even flush their toilets. Not for one second
does it cross their minds where and how that water gets there. Wastewater treatment plants have a difficult job
ensuring they can provide clean and potable water to the public. Nassau County’s “Sewage Treatment Master
Plan” (Sewage Treatment Master Plan, n.d.) has strived to ensure they can provide this service to the people of
Nassau County. However, operating a water treatment plant comes with many challenges. Such as dealing with
emissions and biological products that are inherent in wastewater plants. Additionally, dealing with the power
required to run the plant. Therefore, Nassau County has enlisted Veolia to be tasked with the operation of the
water treatment plant at Cedar Creek. Along with various other sites. A key focus in the operation is to mitigate
unnecessary production of harmful emissions. To do this, providing a means to produce power is needed.
Power Production:
Wastewater treatment plants’ energy consumption varies drastically but can be a detrimental drain from
the grid. Reasons for variation include temperature differences, equipment efficiency, emissions, means of
energy production. The Cedar Creek wastewater plant filters 250034.95 𝑚3 /𝑑𝑎𝑦 of wastewater. To do this, the
plant requires an average power of 5.7 kW. Other wastewater treatment plants operate at around 50,000
BTU/gallon (How Much Energy Does a Wastewater Treatment Plant Use?, 2018). In Figure 1, we can see the
main components at Cedar Creek water treatment plant that require power.
Figure 1: Components that require power at Cedar Creek
Therefore, nearly every wastewater plant has enlisted a means to generate power. If done correctly, the
plant can be fully energy independent. In certain cases, even profiting by selling energy when made in excess
back to the grid. The most common way of powering wastewater plants is to make use of methane production
by biological products. When wastewater is pumped into digester tanks and is treated with microorganisms. The
result is the generation of methane gas that can then be burned to generate heat and electricity (Wastewater
Digester Energy, n.d.). The most common way of doing this is by utilizing an ‘Internal Combustion Engine’
(ICE) in series with a generator. At Cedar Creek, this method is also being implemented.
3
Project Goals:
In an academic setting, various lab apparatuses and precise calibration tools are available. During this
project, one of the previously mentioned engines will serve as our experimental apparatus. We will be analyzing
the engines from a theoretical standpoint. With the goal of having a concrete metric to determine which fuel
blend would yield the highest efficiency from a power and emission perspective. At any given time at least
three engines are running. Since all the engines are the same, we will be analyzing just one (engine 3) and will
apply the findings to the other four. Additionally, we will not be analyzing all the fuels. This is due to a lack of
information on the chemical properties of the digester gas. However, when the information is available, we will
consider the digester gas. Until then, we will be analyzing three baseline cases.
1. Natural gas
2. Natural gas + Diesel (used to combust NG)
3. Diesel
Chapter 2:
In this chapter, we will be presenting a detailed analysis of our engine. The information will be an
amalgamation of engine specifications from the manufacturer. Along with calculating engine parameters from
the data provided from the engine manufacturer.
Engine:
While methane can be burned in any type of ICE. Choosing the right engine can have an enormous
impact on the efficiency of power production. In general, Compression-Ignition (CI) engines are used for
heavier loads. This is due to their higher compression ratios which have a direct relation to efficiency. The
higher the compression ratio, the higher the efficiency (Compression Ignition Engine, 2018). It’s worth noting
that CI engines have much higher temperatures and pressures than Spark-Ignition (SI) engines. Therefore, they
are more expensive because they need to be able to withstand those conditions. At Cedar Creek, we implement
five compression ignition direct injection (CIDI) engines. Additionally, each engine has its respective
turbocharger. This further increases the temperatures and pressures in the engine. The engines have the
capability to run on three different fuels. The fuels are natural gas (NG), diesel fuel (DSL), and our on-site
collected digester gas. The preferred fuel source for the engines is natural gas. This is because the digester gas
can be blended with the natural gas and not diesel. The reason for mixing the digester gas with the natural gas is
to achieve proper combustion while keeping the mechanical components of the engine healthy. When
combusting natural gas or the blend, there is always a little diesel to help start the combustion. Below, Table 1
shows the engine type.
Table 1: Engine type and specs
Type of Engine: Cooper-Bessemer LSVB-12 turbocharged dual fuel engines
Model Number:
LSVB-12GDT
Serial Number:
7238
Type of Turbo:
Cooper-Bessemer ET-18 turbo
Configuration =
V-12
# of Cylinders =
12
4
This engine is also unique in its kinematics. Common engines have a 4-bar linkage. In the engine world,
this linkage is referred to as ‘fork and blade’. However, our engines do not share this. Their linkage is referred
to as an ‘articulated rod’. This is where there is a second connecting rod mounted to the first connecting rod.
This can be illustrated below.
Image 1: Variant connecting rod
Engine Data:
An integral portion of information when analyzing engines is the overall geometry. This is because with
the appropriate geometry we can normalize the engine to get parameters on a cylinder and cycle basis.
Table 2: Engine geometry per cylinder
Connecting rod length:
l = 1.097562
m
Given
Bore:
b = 0.393701
m
Given
Stroke:
s = 0.558801
m
Given
Crank arm:
a = 0.279401
m
Given
unitless
Given
Compression ratio:
r=
11.10
Displacement Volume: 𝑉𝑑 = 0.068027
Clearance Volume:
𝑉𝑐 =
0.006735
Total Volume: 𝑉𝑡 = 0.074762
𝑚3
𝑐𝑦𝑙
𝑚3
𝑐𝑦𝑙
𝑚3
𝑐𝑦𝑙
𝜋 ∗ 𝑠 ∗ (𝑏 2 )
4
𝑉𝑑
𝑉𝑐 =
(𝑟 − 1)
𝑉𝑑 =
𝑉𝑡 = 𝑉𝑑 + 𝑉𝑐
We were also given our brake mean effective pressure (BMEP). With this, we can calculate other engine
performance parameters which will be crucial when going through our power cycles.
Table 3: Engine brake parameters
Brake mean effective pressure: BMEP = 95.38
Brake work:
𝑊𝑏 =
6.49
Brake work per revolution:
𝑊𝑅 =
3.24
kPa
Per cylinder
kJ/cycle 𝑊𝑏 = 𝐵𝑀𝐸𝑃 ∗ 𝑉𝑑
𝑊𝑏
kJ/rev
𝑊𝑅 =
𝑛𝑅
5
Brake power:
𝑃𝑏 =
21.63 W/cycle
Brake torque:
𝜏𝑏 =
0.52
kJ/rev
𝑃𝑏 = 𝑊𝑏 ∗
𝜏𝑏 =
𝑁
𝑛𝑅
𝑊𝑅
(2 ∗ 𝜋)
With the assistance of Joe Koch, Diesel manager at Cedar Creek. We are given engine intake and exhaust
temperature and pressures. This will be integral as it is the starting point of our pV diagram (power cycle).
Using the appropriate thermodynamic relationships and processes, we can generate plot pressure as a function
of volume.
Table 4: Input and Output engine parameters
Intake Temperature: 𝑇1 =
37.78
𝑇1 = 𝑇𝑖𝑛𝑡𝑎𝑘𝑒
°C
Intake Pressure: 𝑝1 = 160.57 kPa 𝑝1 = (17.5"𝐻𝑔 + 𝑝𝑎𝑡𝑚 ) ∗ (𝐶𝐹 𝑡𝑜 𝑘𝑃𝑎)
Exhaust Temperature: 𝑇4 = 493.33
𝑇4 = 𝑇𝑒𝑥ℎ𝑎𝑢𝑠𝑡
°C
Exhaust Pressure: 𝑝4 = 167.85 kPa
𝑝4 = (19.65"Hg + 𝑝𝑎𝑡𝑚 )*(CF to kPa)
Chapter 3:
In this chapter, we will introduce the various types of fuel usage. From the fuel usage, we will determine
our air to fuel ratio (A/F). Using the A/F ratio, and thermodynamic principles. We will generate our power
cycle, and an array of other engine parameters that can be used to evaluate the engine.
Fuel Properties:
To determine the mass of natural gas and diesel, we require the density. Furthermore, later when determining
the power cycles and engine parameters for these fuels, we require other fuel properties. The two main sources
of fuel properties are as follows:
•
‘The Engineering Toolbox’ (Gases - Ratios of Specific Heat, 2003)
•
Table D.4 in the textbook used in MEC 523 (Heywood, 2000).
Image 2: Table D.4-Fuel Properties (Heywood,2000)
6
Having these properties allows us to do two major things. The first is to calculate the fuel mass usage per cycle
given volume usage. The second is to calculate the heat addition during combustion given mass of fuel usage.
Usage per Cycle:
Air:
To have combustion, we require fuel and a source of oxygen. Generally, oxygen comes from air in
ICE’s. To determine the mass of air used per cycle and cylinder. We need to make use of engine geometry and
the ‘Ideal Gas Law’ (Ideal Gas Law, n.d.). First, we assume that on the intake of the engine, most of the
cylinder will be filled with air. In our case, our engine is boosted. So, the air will be pressurized. We assume
95% volumetric efficiency as the engine is boosted.
𝑉𝑎𝑖𝑟 = 𝑉𝑑 ∗ (95%)
Then by using the ideal gas las to determine the density of the air. We can determine the mass of the air
used per cylinder and cycle. Doing this brings us a step closer to calculating the A/F ratio.
Table 5: Air mass calculations
R for air:
R=
0.287
kJ/(kg*K)
Given
Intake Temp: Tintake =
310.93
K
Given
Intake pressure: pintake =
160.57
kPa
Given
Volume of air: Vintake =
0.071024
𝑚3
Vintake = Vair
3
Density of air @T_intake:
ρair =
1.80
kg/𝑚
ρair = pintake /(R ∗ Tintake )
mass of air:
m1 =
0.12780
kg/cycle
mair = ρair ∗ Vintake
Mass of air per cycle:
mair =
0.127797
kg/cycle
mair = m1
Natural Gas:
Unlike calculating the mass of air, determining the mass of natural gas is a bit more complicated. Using
the annual fuel usage of natural gas coupled with annual engine runtime (Table 6). We averaged the data to a
monthly, then daily period. This can be seen in Table 7.
Table 6: 2021 Natural Gas Consumption by Engine 3
Year of 2021: Engine #3 Run Hours Natural gas used [10^6 scf]
January
667.00
42.41
February
647.00
40.14
March
722.00
43.70
April
718.00
39.12
May
708.00
37.35
June
674.00
35.38
July
309.00
38.09
August
818.00
37.96
September
699.00
36.63
7
October
710.00
26.42
November
683.00
25.76
December
691.00
25.28
Table 7: Average NG runtime and usage
Time period: Engine 3 Run seconds [s] Natural gas used [m^3]
Monthly:
Daily:
2,413,800.00
336,833.58
80,460.00
11,227.79
Once we determined the daily runtime of the engine. We can use the angular speed of the crankshaft to
determine the number of cycles per second our engine produces. This is a crucial number to determine the fuel
usage per cycle.
Table 8: Calculation to get number of cycles per day
Angular Speed:
ω=
400.00
RPM
Given
Rotational speed of crankshaft:
N=
6.67
rev/s
N = ω/60
Number of crank revs per cycle:
𝑛𝑅 =
2.00
Cycles per second:
𝐶𝑦𝑐𝑠 =
3.33
Daily runtime:
t=
80,460.00
Daily cycles per day: 𝑁𝑐𝑦𝑐𝑙𝑒𝑠 = 268,200.00
rev/cycle for 4-stroke engines, 𝑛𝑅 = 2
𝑁
cycles/s
𝐶𝑦𝑐𝑠 =
𝑛𝑅
s/day
Average day = 22.35 hours
cycles
𝑁𝑐𝑦𝑐𝑙𝑒𝑠 = 𝐶𝑦𝑐𝑠 ∗ 𝑡
By dividing the daily usage of natural gas per cylinder by the number of cycles per day. We can get the volume
of natural gas usage per cycle. Then by multiplying the density of natural gas, we can get the mass of natural
gas used per cycle. With the natural gas mass, we can get out air to fuel ratio for natural gas.
Table 9: Natural gas usage per cycle
Daily NG Usage per cylinder: 𝑉𝑁𝐺,𝑑 =
935.65
Daily cycles per day: 𝑁𝑐𝑦𝑐𝑙𝑒𝑠 = 268,200.00
𝑚3 /cylinder Daily NG usage/12
cycles
NG used per cycle:
𝑉𝑁𝐺 =
0.0034886
𝑚3 /cycle
Mass of NG per cycle:
𝑚𝑁𝐺 =
0.002501
kg/cycle
𝑉𝑁𝐺,𝑑
𝑁𝑐𝑦𝑐𝑙𝑒𝑠
= 𝑉𝑁𝐺 ∗ 𝜌𝑁𝐺
𝑉𝑁𝐺 =
𝑚𝑁𝐺
Diesel:
Determining the number of cycles per day allows us to easily determine the mass of any fuel used given
its daily volume. As a reminder, a small amount of diesel is used on every cycle of natural gas to begin
combustion. However, there are instances where the engines must run fully on diesel. We will be considering
both scenarios in this section.
8
NG-DSL:
When running NG-DSL, the daily consumption for diesel by each engine is 73.33 gallons/day.
Dividing that daily consumption by the number of cylinders gives us the daily amount of diesel used per
cylinder. Similarly, to natural gas, the procedure to determine the mass of diesel used is as follows:
Table 10: DSL consumed with NG
Daily DSL Usage per cylinder:
𝑉𝐷𝑆𝐿,𝑑 =
𝑚3 /cylinder Daily DSL usage/12
0.0231
Daily cycles per day: 𝑁𝑐𝑦𝑐𝑙𝑒𝑠 = 268,200.00
DSL used per cycle:
cycles
𝑚3 /cycle
𝑉𝐷𝑆𝐿 =
0.0000001
Mass of DSL per cycle:
𝑚𝐷𝑆𝐿 =
kg/cycle
0.0000706
𝑉𝐷𝑆𝐿,𝑑
𝑁𝑐𝑦𝑐𝑙𝑒𝑠
= 𝑉𝐷𝑆𝐿 ∗ 𝜌𝐷𝑆𝐿
𝑉𝐷𝑆𝐿 =
𝑚𝐷𝑆𝐿
DSL:
When fully running DSL, we are given a volumetric flowrate of 300 gallons/hr. Multiplying this
flowrate by the density of diesel gives us the mass flowrate. Then by dividing the mass flowrate by the
cycles per second of the engine. We get the mass usage per cycle.
Table 11: DSL consumed
Diesel Consumption rate
Per cylinder:
𝑉̇𝐷𝑆𝐿 =
0.000026285
Diesel mass flow rate: 𝑚̇𝐷𝑆𝐿 =
0.021505
Mass of DSL per cycle: 𝑚𝐷𝑆𝐿 =
0.0064516
𝑚3
𝑔𝑎𝑙𝑙
ℎ𝑟
𝑉̇𝐷𝑆𝐿,𝑑 =
12
kg/cycle 𝑚̇𝐷𝑆𝐿,𝑑 = 𝑉̇𝐷𝑆𝐿,𝑑 ∗ 𝜌𝐷𝑆𝐿
𝑚̇𝐷𝑆𝐿
kg/cycle
𝑚𝐷𝑆𝐿 =
𝐶𝑦𝑐𝑠
300
A/F Ratio:
Now that we have determined the mass of air, natural gas, and diesel for all scenarios. We can begin to
compute our air to fuel ratios for every fuel selection. The A/F ratio will serve as one of the initial conditions
when generating our power cycle.
Table 12: A/F ratios
For only NG, mass of fuel:
𝑚𝑓,𝑁𝐺 =
0.002501 kg/cycle
For DSL-NG, mass of fuel:
𝑚𝑓,𝐷𝑆𝐿−𝑁𝐺 =
0.002572 kg/cycle
𝑚𝑓,𝐷𝑆𝐿 =
0.006452 kg/cycle
For DSL, mass of fuel:
Mass of air:
Total mass with NG:
Total mass with DSL-NG:
Total mass with DSL:
A/F for NG:
𝑚𝑎𝑖𝑟 =
0.12780
kg/cycle
𝑚𝑡𝑡𝑙,𝑁𝐺 =
0.13030
kg/cycle
𝑚𝑡𝑡𝑙,𝐷𝑆𝐿−𝑁𝐺 =
0.13037
kg/cycle
𝑚𝑡𝑡𝑙,𝐷𝑆𝐿 =
𝐴
( ) =
𝐹 𝑁𝐺
0.13425
kg/cycle
51.09
LEAN!!
9
A/F for DSL-NG:
A/F for DSL:
𝐴
( )
=
𝐹 (𝐷𝑆𝐿−𝑁𝐺)
49.69
LEAN!!
𝐴
19.81
LEAN!!
(𝐹 )
𝐷𝑆𝐿
=
As can be seen in Image 3 from the slides from MEC 523 (Chapter 2, pg. 20), the calculated A/F ratios
are within range for a CIDI engine. Notably, the engines are running lean. This makes sense as the engine is
coupled with a turbocharger.
Image 3: A/F ratio range
Power cycle and Engine Parameters:
Once we have determined the air to fuel ratio. We have determined the fuel input parameters. However,
there are a few other details we require. We need the intake temperature and pressure, a cycle to model our
power cycle after, and the instantaneous volume of the cylinder. Fortunately, we already have intake
temperature and pressure. Since our engine is a CIDI diesel engine. We will be using a constant pressure cycle
(AKA: a diesel cycle) as a model for our engine. Below, we will calculate our instantaneous volume, and later
calculate our power cycle for every fuel.
Constant Pressure Cycle:
A constant pressure cycle is a type of thermodynamic cycle which follows certain behaviors. Essentially,
the compression and expansion strokes follow an isentropic relationship. This is also common with constant
volume, or limited pressure cycles. However, the main distinction is that the fuel energy is added following an
isobaric process (constant pressure). This can be seen from states 2 to 3 in Image 4.
10
Image 4: Constant pressure cycle (Diesel Cycle, 2022)
Instantaneous Volume:
Since our engine is a 4-stroke engine. We know that there are two revolutions per cycle. That means the
720°
crankshaft rotates 𝑐𝑦𝑐𝑙𝑒. As the crankshaft spins at this rate, the volume and pressure of our cylinder changes as
well.
Image 5: Cylinder Kinematics
Image 5 depicts a cylinder, and how the volume changes as a function of x. Which is the linear motion of the
piston in the cylinder. The linear motion of the piston, x, is a function of crank angle degrees. The equation for
x is strictly a mathematical relationship and can be seen in Image 6.
Image 6: Equation for piston linear motion
As we change our crank angle degrees by increments of 0.1. Our piston linear motion will change. Applying
this linear motion to Image 7, will give us the instantaneous volume as a function of crank angle degrees. For a
detailed table of the variables used in these equations, refer to Table 2.
11
Image 7: Instantaneous volume of cylinder
Natural Gas:
Using the A/F ratio for NG calculated previously, engine geometry, and thermodynamic principles. We
first map out the closed portion of our power cycle. The closed portion is simply the parts of the power cycle
which are compressing and expanding the fuel mix. In other words, everything except the intake and exhaust
portions. In Table 13, we can see the closed portion of the natural gas constant pressure loop.
Table 13: Closed loop states for NG
State 1:
Pressure:
𝑝1 =
160.57
kPa
3
𝑚
GIVEN
𝑉1 = 𝑉𝑡 =
𝑚 ∗ 𝑅 ∗ 𝑇1
𝑝1
Volume:
𝑉1 =
0.07
Temperature:
𝑇1 =
37.78
°C
GIVEN
Pressure:
𝑝2 =
3,371.71
kPa
𝑝2 = 𝑝1 ∗ 𝑟 𝛾
Volume:
𝑉2 =
0.01
𝑚3
𝑉2 = 𝑉𝑐
Temperature:
𝑇2 =
71.47
°C
𝑇2 = 𝑇1 ∗ 𝑟 𝛾−1
𝑝3 =
3,371.71
kPa
Isobaric
0.0083439165
3
State 2:
State 3:
Pressure:
Volume:
Temperature:
𝑉3 =
𝑇3 =
440.64
𝑚
°C
𝑉3 =
𝑚 ∗ 𝑅 ∗ 𝑇3
𝑝3
𝑇3 = 𝑇2 +
𝑄𝑎𝑑𝑑
(𝑚 ∗ 𝑐𝑝 )
State 4:
𝑝4 =
Pressure:
𝑝4 =
210.53
kPa
Volume:
𝑉4 =
0.07
𝑚3
𝑉4 = 𝑉1
𝑇4 =
Temperature:
𝑇4 =
246.52
°C
𝑝3
𝑉 𝛾
(𝑉4 )
3
𝑇3
𝑉 𝛾−1
(𝑉4 )
3
12
To generate our values for pressure as a function of volume. We need to make use of certain thermodynamic
principles. As mentioned previously, the compression stroke and intake stroke both follow an isentropic
behavior. Due to our cycle being modeled as a constant pressure cycle. We know that from states 2 to 3 the
pressure will be constant. Then, from states 4 to 1, we have an isochoric (constant volume) heat rejection. To
generate our values for pressure as a function of volume we apply these principles. Additionally, since we know
the pressures at state 1 and 4. We can bridge the closed portion of our loop with our pumping loop. This will
result in the following power cycle for natural gas:
PV Diagram per cylinder for NG
4,000
3,500
Pressure [kPa]
3,000
2,500
2,000
1,500
1,000
500
0
0.000
0.010
0.020
0.030
0.040
0.050
0.060
0.070
0.080
Volume [m^3]
Figure 2: pV diagram for natural gas
Following the construction of our pV diagram. We can then utilize the trapezoid rule (Trapezoid rule, 2022) to
calculate the area under the curve. The area of the curves of the closed portion of the pV diagram correlate to
the energy generated in the closed portion of the loop. This is referred to as ‘gross work’. The area of the curves
in the pumping loop correlates to the energy expended or gained in the loop. This is referred to as ‘pump work’.
Since our engine is boosted, the pumping loop will contribute to our energy output. From this information, we
can calculate an array of other engine performance parameters for NG as seen in Table 14.
Table 14: Engine parameters on natural gas
Heat addition from fuel:
𝑄𝑎𝑑𝑑 =
112.56
kJ/cycle
𝑄𝑎𝑑𝑑 = 𝑚𝑓 ∗ 𝐿𝐻𝑉
Work of isentropic compression
stroke:
Work of Isobaric expansion
stroke:
Work of isentropic expansion
stroke:
Heat rejection:
𝑊1−2 =
-8.12
kJ/cycle
𝑊1−2 = 𝑚𝑐𝑣 (𝑇1 − 𝑇2 )
𝑊2−3 =
0.71
kJ/cycle
𝑊2−3 = 𝑚 ∗ 𝑝2 (𝑉3 − 𝑉2 )
𝑊3−4 =
46.79
kJ/cycle
𝑊3−4 = 𝑚 ∗ 𝑐𝑣 (𝑇3 − 𝑇4 )
𝑄4−1 =
-50.32
kJ/cycle
𝑄4−1 = 𝑚 ∗ 𝑐𝑣 (𝑇1 − 𝑇4 )
Gross Work:
𝑊𝑖𝑔 =
11.80
kJ/cycle
Pumping Work:
𝑊𝑝 =
-4.11
kJ/cycle
Net Work:
𝑊𝑖𝑛 =
15.91
kJ/cycle
Gross work is sum of area of
Compression & Expansion loop
Pump work is sum of area under
curve of intake & exhaust loop
𝑊𝑖𝑛 = 𝑊𝑖𝑔 − 𝑊𝑝
𝐼𝑀𝐸𝑃𝑛 =
233.85
kPa
𝐼𝑀𝐸𝑃𝑛 = 𝐼𝑀𝐸𝑃𝑔 − 𝑃𝑀𝐸𝑃
Net Indicated mean effective
pressure:
13
173.47
kPa
𝐼𝑀𝐸𝑃𝑔 = 𝑊𝑖𝑔 /𝑉𝑑
𝑃𝑀𝐸𝑃 =
-60.38
kPa
𝑃𝑀𝐸𝑃 = 𝑊𝑝 /𝑉𝑑
𝐹𝑀𝐸𝑃 =
138.47
kPa
𝐹𝑀𝐸𝑃 = 𝐼𝑀𝐸𝑃𝑛 − 𝐵𝑀𝐸𝑃
Work of Friction:
𝑊𝑓 =
9.42
kPa
𝑊𝑓 = 𝐹𝑀𝐸𝑃 ∗ 𝑉𝑑
Gross indicated Power:
𝑃𝑖𝑔 =
39.33
W
𝑃𝑖𝑔 = (𝑁 ∗ 𝑊𝑖𝑔 )/𝑛𝑅
Pumping power:
𝑃𝑝 =
-13.69
W
𝑃𝑝 = (𝑁 ∗ 𝑊𝑝 )/𝑛𝑅
Friction power:
𝑃𝑓 =
31.40
W
𝑃𝑓 = (𝑁 ∗ 𝑊𝑓 )/𝑛𝑅
Thermal Indicated Gross
efficiency:
Combustion Efficiency:
𝜂𝑡ℎ,𝑖𝑔 =
55.30
%
𝜂𝑡ℎ,𝑖𝑔 = (1 + 𝑄4 −1 /𝑄𝑎𝑑𝑑 )
𝜂𝑐 =
95.00
%
Assume 95%
Gross Indicated Fuel Conversion
efficiency:
Net Indicated Fuel Conversion
efficiency:
Thermal Indicated net efficiency:
𝜂𝑓,𝑖𝑔 =
10.48
%
𝜂𝑓,𝑖𝑔 = 𝑊𝑖𝑔 /𝑄𝑎𝑑𝑑
𝜂𝑓,𝑖𝑛 =
14.13
%
𝜂𝑓,𝑖𝑛 = 𝑊𝑖𝑛 /𝑄𝑎𝑑𝑑
𝜂𝑡ℎ,𝑖𝑛 =
14.88
%
𝜂𝑡ℎ,𝑖𝑛 = 𝜂𝑓,𝑖𝑛 /𝜂𝑐
𝜂𝑓,𝑏 =
5.76
%
𝜂𝑓,𝑏 = 𝑊𝑏 /𝑄𝑎𝑑𝑑
𝜂𝑚 =
40.79
%
𝜂𝑚,𝑆𝐴𝐸 =
54.99
%
𝜂𝑚 = (1 − (𝑃𝑓 /(𝑃𝑖𝑔 − 𝑃𝑝 ))
∗ 100%
𝜂𝑚,𝑆𝐴𝐸 = (1 − ((𝑃𝑝 + 𝑃𝑓 )/𝑃𝑖𝑔 ))
∗ 100%
Gross indicated mean effective
pressure:
Pumping mean effective pressure:
Friction mean effective pressure:
Brake Fuel Conversion
efficiency:
Mechanical efficiency:
SAE Mechanical efficiency:
I𝐼𝑀𝐸𝑃𝑔 =
NG-DSL:
Using the A/F ratio for NG-DSL calculated previously, engine geometry, and thermodynamic principles.
We take the same analysis done on NG, to NG-DSL. In Table 15, we can see the closed portion of the natural
gas and diesel constant pressure loop.
Table 15: Closed loop states for NG-DSL
State 1:
Pressure:
𝑝1 =
160.568
kPa
3
𝑚
GIVEN
𝑉1 = 𝑉𝑡 =
𝑚 ∗ 𝑅 ∗ 𝑇1
𝑝1
Volume:
𝑉1 =
0.074762
Temperature:
𝑇1 =
37.777778
°C
GIVEN
Pressure:
𝑝2 =
3371.708106
kPa
𝑝2 = 𝑝1 ∗ 𝑟 𝛾
Volume:
𝑉2 =
0.006735
𝑚3
𝑉2 = 𝑉𝑐
Temperature:
𝑇2 =
71.467030
°C
𝑇2 = 𝑇1 ∗ 𝑟 𝛾−1
State 2:
State 3:
14
Pressure:
Volume:
Temperature:
𝑝3 =
3371.708106
kPa
𝑉3 =
0.008533965128
55548
3
𝑇3 =
450.433038
𝑚
Isobaric
𝑉3 =
𝑚 ∗ 𝑅 ∗ 𝑇3
𝑝3
𝑇3 = 𝑇2 +
°C
𝑄𝑎𝑑𝑑
(𝑚 ∗ 𝑐𝑝 )
State 4:
𝑝4 =
Pressure:
𝑝4 =
216.608908
kPa
Volume:
𝑉4 =
0.074762
𝑚3
𝑉4 = 𝑉1
𝑇4 =
Temperature:
𝑇4 =
253.505295
𝑝3
𝑉4 𝛾
(𝑉 )
3
°C
𝑇3
𝑉 𝛾−1
(𝑉4 )
3
PV Diagram per cylinder for NG-DSL
4,000
3,500
Pressure [kPa]
3,000
2,500
2,000
1,500
1,000
500
0
0.000
0.010
0.020
0.030
0.040
0.050
0.060
0.070
0.080
Volume [m^3]
Figure 3: pV diagram for NG-DSL
Notice how the NG and NG-DSL pV diagrams are almost identical. This can be attributed to the minimal fuel
input of diesel. This is made apparent by looking at the difference in 𝑄𝑎𝑑𝑑 . We can calculate an array of other
engine performance parameters for NG-DSL as seen in Table 16.
Table 16: Engine parameters on natural gas
Heat addition from fuel:
𝑄𝑎𝑑𝑑 =
Work of isentropic compression
stroke:
𝑊1−2 =
115.608730
kJ/cycle
𝑄𝑎𝑑𝑑 = 𝑚𝑓 ∗ 𝐿𝐻𝑉
kJ/cycle
𝑊1−2 = 𝑚𝑐𝑣 (𝑇1 − 𝑇2 )
-8.125267
15
Work of Isobaric expansion
stroke:
Work of isentropic expansion
stroke:
Heat rejection:
Gross Work:
𝑊2−3 =
kJ/cycle
𝑊2−3 = 𝑚 ∗ 𝑝2 (𝑉3 − 𝑉2 )
kJ/cycle
𝑊3−4 = 𝑚 ∗ 𝑐𝑣 (𝑇3 − 𝑇4 )
kJ/cycle
𝑄4−1 = 𝑚 ∗ 𝑐𝑣 (𝑇1 − 𝑇4 )
kJ/cycle
kJ/cycle
Gross work is sum of area of
Compression & Expansion loop
Pump work is sum of area under
curve of intake & exhaust loop
𝑊𝑖𝑛 = 𝑊𝑖𝑔 − 𝑊𝑝
kPa
𝐼𝑀𝐸𝑃𝑛 = 𝐼𝑀𝐸𝑃𝑔 − 𝑃𝑀𝐸𝑃
kPa
𝐼𝑀𝐸𝑃𝑔 = 𝑊𝑖𝑔 /𝑉𝑑
0.790623
𝑊3−4 =
47.495575
𝑄4−1 =
-52.029756
𝑊𝑖𝑔 =
13.14
Pumping Work:
𝑊𝑝 =
kJ/cycle
-4.54
Net Work:
𝑊𝑖𝑛 =
17.68
𝐼𝑀𝐸𝑃𝑛 =
Net Indicated mean effective
pressure:
Gross indicated mean effective
pressure:
Pumping mean effective pressure:
𝐼𝑀𝐸𝑃𝑔 =
𝑃𝑀𝐸𝑃 =
-66.76
kPa
𝑃𝑀𝐸𝑃 = 𝑊𝑝 /𝑉𝑑
Friction mean effective pressure:
𝐹𝑀𝐸𝑃 =
164.58
kPa
𝐹𝑀𝐸𝑃 = 𝐼𝑀𝐸𝑃𝑛 − 𝐵𝑀𝐸𝑃
Work of Friction:
𝑊𝑓 =
11.20
kPa
𝑊𝑓 = 𝐹𝑀𝐸𝑃 ∗ 𝑉𝑑
Gross indicated Power:
𝑃𝑖𝑔 =
43.81
W
𝑃𝑖𝑔 = (𝑁 ∗ 𝑊𝑖𝑔 )/𝑛𝑅
Pumping power:
𝑃𝑝 =
-15.14
W
𝑃𝑝 = (𝑁 ∗ 𝑊𝑝 )/𝑛𝑅
Friction power:
𝑃𝑓 =
37.32
W
𝑃𝑓 = (𝑁 ∗ 𝑊𝑓 )/𝑛𝑅
%
𝜂𝑡ℎ,𝑖𝑔 = (1 + 𝑄4 −1 /𝑄𝑎𝑑𝑑 )
%
Assume 95%
%
𝜂𝑓,𝑖𝑔 = 𝑊𝑖𝑔 /𝑄𝑎𝑑𝑑
%
𝜂𝑓,𝑖𝑛 = 𝑊𝑖𝑛 /𝑄𝑎𝑑𝑑
%
𝜂𝑡ℎ,𝑖𝑛 = 𝜂𝑓,𝑖𝑛 /𝜂𝑐
%
𝜂𝑓,𝑏 = 𝑊𝑏 /𝑄𝑎𝑑𝑑
%
𝜂𝑚 = (1 − (𝑃𝑓 /(𝑃𝑖𝑔 − 𝑃𝑝 ))
∗ 100%
𝜂𝑚,𝑆𝐴𝐸 = (1 − ((𝑃𝑝 + 𝑃𝑓 )/𝑃𝑖𝑔 ))
∗ 100%
259.96
193.20
Thermal Indicated Gross
efficiency:
Combustion Efficiency:
𝜂𝑡ℎ,𝑖𝑔 =
Gross Indicated Fuel Conversion
efficiency:
Net Indicated Fuel Conversion
efficiency:
Thermal Indicated net efficiency:
𝜂𝑓,𝑖𝑔 =
Brake Fuel Conversion
efficiency:
Mechanical efficiency:
54.99
𝜂𝑐 =
95.00
11.37
𝜂𝑓,𝑖𝑛 =
15.30
𝜂𝑡ℎ,𝑖𝑛 =
16.10
𝜂𝑓,𝑏 =
5.61
𝜂𝑚 =
36.69
SAE Mechanical efficiency:
𝜂𝑚,𝑆𝐴𝐸 =
%
49.37
16
DSL:
Using the A/F ratio for DSL calculated previously, engine geometry, and thermodynamic principles. We
take the same analysis done on NG, to DSL. In Table 17, we can see the closed portion of the natural gas and
diesel constant pressure loop.
Table 17: Closed loop states for NG-DSL
State 1:
Pressure:
𝑝1 =
160.57
kPa
GIVEN
𝑉1 = 𝑉𝑡 =
𝑚 ∗ 𝑅 ∗ 𝑇1
𝑝1
Volume:
𝑉1 =
0.07
𝑚3
Temperature:
𝑇1 =
37.78
°C
GIVEN
Pressure:
𝑝2 =
3,669.25
kPa
𝑝2 = 𝑝1 ∗ 𝑟 𝛾
Volume:
𝑉2 =
0.01
𝑚3
𝑉2 = 𝑉𝑐
Temperature:
𝑇2 =
77.77
°C
𝑇2 = 𝑇1 ∗ 𝑟 𝛾−1
𝑝3 =
3,669.25
kPa
Isobaric
0.02
3
State 2:
State 3:
Pressure:
Volume:
Temperature:
𝑉3 =
𝑇3 =
1,816.65
𝑚
°C
𝑉3 =
𝑚 ∗ 𝑅 ∗ 𝑇3
𝑝3
𝑇3 = 𝑇2 +
𝑄𝑎𝑑𝑑
(𝑚 ∗ 𝑐𝑝 )
State 4:
𝑝4 =
Pressure:
𝑝4 =
621.47
kPa
Volume:
𝑉4 =
0.07
𝑚3
𝑉4 = 𝑉1
𝑇4 =
Temperature:
𝑇4 =
1,205.90
°C
𝑝3
𝑉 𝛾
(𝑉4 )
3
𝑇3
𝑉 𝛾−1
(𝑉4 )
3
17
PV Diagram per cylinder for DSL
4,000
3,500
Pressure [kPa]
3,000
2,500
2,000
1,500
1,000
500
0
0.000
0.010
0.020
0.030
0.040
0.050
0.060
0.070
0.080
Volume [m^3]
Figure 4: pV diagram for DSL
Notice how the DSL pV diagram differs greatly from that of NG or NG-DSL. This can be attributed to higher
energy release from the fuel input of diesel. This is made apparent by looking at the difference in 𝑄𝑎𝑑𝑑 . We can
calculate an array of other engine performance parameters for DSL as seen in Table 18.
Table 18: Engine parameters on natural gas
Heat addition from fuel:
𝑄𝑎𝑑𝑑 =
Work of isentropic compression
stroke:
Work of Isobaric expansion
stroke:
Work of isentropic expansion
stroke:
Heat rejection:
𝑊1−2 =
290.32
kJ/cycle
𝑄𝑎𝑑𝑑 = 𝑚𝑓 ∗ 𝐿𝐻𝑉
kJ/cycle
𝑊1−2 = 𝑚𝑐𝑣 (𝑇1 − 𝑇2 )
kJ/cycle
𝑊2−3 = 𝑚 ∗ 𝑝2 (𝑉3 − 𝑉2 )
kJ/cycle
𝑊3−4 = 𝑚 ∗ 𝑐𝑣 (𝑇3 − 𝑇4 )
kJ/cycle
𝑄4−1 = 𝑚 ∗ 𝑐𝑣 (𝑇1 − 𝑇4 )
kJ/cycle
kJ/cycle
Gross work is sum of area of
Compression & Expansion loop
Pump work is sum of area under
curve of intake & exhaust loop
𝑊𝑖𝑛 = 𝑊𝑖𝑔 − 𝑊𝑝
kPa
𝐼𝑀𝐸𝑃𝑛 = 𝐼𝑀𝐸𝑃𝑔 − 𝑃𝑀𝐸𝑃
kPa
𝐼𝑀𝐸𝑃𝑔 = 𝑊𝑖𝑔 /𝑉𝑑
-5.14
𝑊2−3 =
6.08
𝑊3−4 =
78.44
𝑄4−1 =
Gross Work:
𝑊𝑖𝑔 =
Pumping Work:
𝑊𝑝 =
Net Work:
𝑊𝑖𝑛 =
-150.02
81.36
kJ/cycle
-33.45
114.80
Net Indicated mean effective
pressure:
Gross indicated mean effective
pressure:
Pumping mean effective pressure:
𝐼𝑀𝐸𝑃𝑛 =
𝑃𝑀𝐸𝑃 =
-491.67
kPa
𝑃𝑀𝐸𝑃 = 𝑊𝑝 /𝑉𝑑
Friction mean effective pressure:
𝐹𝑀𝐸𝑃 =
1,592.23
kPa
𝐹𝑀𝐸𝑃 = 𝐼𝑀𝐸𝑃𝑛 − 𝐵𝑀𝐸𝑃
Work of Friction:
𝑊𝑓 =
108.31
kPa
𝑊𝑓 = 𝐹𝑀𝐸𝑃 ∗ 𝑉𝑑
Gross indicated Power:
𝑃𝑖𝑔 =
271.19
W
𝑃𝑖𝑔 = (𝑁 ∗ 𝑊𝑖𝑔 )/𝑛𝑅
Pumping power:
𝑃𝑝 =
-111.49
W
𝑃𝑝 = (𝑁 ∗ 𝑊𝑝 )/𝑛𝑅
1,687.61
I𝐼𝑀𝐸𝑃𝑔 =
1,195.94
18
Friction power:
𝑃𝑓 =
Thermal Indicated Gross
efficiency:
Combustion Efficiency:
𝜂𝑡ℎ,𝑖𝑔 =
Gross Indicated Fuel Conversion
efficiency:
Net Indicated Fuel Conversion
efficiency:
Thermal Indicated net efficiency:
𝜂𝑓,𝑖𝑔 =
Brake Fuel Conversion
efficiency:
Mechanical efficiency:
361.05
W
𝑃𝑓 = (𝑁 ∗ 𝑊𝑓 )/𝑛𝑅
%
𝜂𝑡ℎ,𝑖𝑔 = (1 + 𝑄4 −1 /𝑄𝑎𝑑𝑑 )
%
Assume 95%
%
𝜂𝑓,𝑖𝑔 = 𝑊𝑖𝑔 /𝑄𝑎𝑑𝑑
%
𝜂𝑓,𝑖𝑛 = 𝑊𝑖𝑛 /𝑄𝑎𝑑𝑑
%
𝜂𝑡ℎ,𝑖𝑛 = 𝜂𝑓,𝑖𝑛 /𝜂𝑐
%
𝜂𝑓,𝑏 = 𝑊𝑏 /𝑄𝑎𝑑𝑑
%
𝜂𝑚 = (1 − (𝑃𝑓 /(𝑃𝑖𝑔 − 𝑃𝑝 ))
∗ 100%
𝜂𝑚,𝑆𝐴𝐸 = (1 − ((𝑃𝑝 + 𝑃𝑓 )/𝑃𝑖𝑔 ))
∗ 100%
48.33
𝜂𝑐 =
95.00
28.02
𝜂𝑓,𝑖𝑛 =
39.54
𝜂𝑡ℎ,𝑖𝑛 =
41.62
𝜂𝑓,𝑏 =
2.23
𝜂𝑚 =
5.65
SAE Mechanical efficiency:
𝜂𝑚,𝑆𝐴𝐸 =
%
7.98
Power Produced:
When you take the net-work of each cycle and expand that to encompass the entire engine. We can
determine the net power the engine produces on each respective fuel.
𝑃𝑛 = 𝑊𝑖𝑛 ∗ #𝑐𝑦𝑙 ∗ 𝐶𝑦𝑐𝑠
Table 19: Power output for each fuel
Net Power of engine for NG:
𝑃𝑛,𝑁𝐺 =
636.31
kW
Net Power of engine for NG-DSL: 𝑃𝑛,𝑁𝐺−𝐷𝑆𝐿 = 707.38
kW
Net Power of engine for DSL:
𝑃𝑛,𝐷𝑆𝐿 =
4,592.11 kW
The engines at Cedar Creek have been derated to around 1700kW-2400kW. Reasons for the lack of power for
natural gas can be attributed to lack of exact fuel inputs. Additionally, calculated max pressure is significantly
lower than actual recorded max pressure. This has a direct effect on power produced. Solutions to minimize this
differential will be presented in Chapter 5. Regarding diesel, the power output is greater than actual power. This
is likely why the engines have been derated. The pressures and power output on running full diesel deteriorated
the lifecycle of the engine.
Chapter 4:
In this chapter we will choose a cycle from Chapter 3. We will first conduct a chemical balance for
natural gas. Then we will run natural gas and diesel cycles through the GREET software (GREET Software,
2022). This will serve as a model for the fuel of choice and its effects on the environment. Additionally, a Life
Cycle Analysis (LCA) will show us the effect a product has from how it was sourced to then being used, or
‘well-to-pump’.
Chemical Balance:
In this section, we will conduct a chemical balance on natural gas. We will be conducting the balance on
natural gas using methane. This is because over 92% of natural gas is methane. So, it is a fair comparison. The
19
two notable results of a chemical balance. The first is that you can get the air-fuel ratio at stoichiometric (stoich)
conditions. This is when there is just enough air to fuel. The second is with the stoich air to fuel ratio and the
actual air to fuel ratio. We can calculate the equivalency ratio. That is a metric that can compare if the engine is
running lean or rich. We already know our engine is running lean, but we don’t know how lean. This chemical
balance allows us to determine that information. We will conduct this balance on a singular mole of fuel. That
way it can be scaled to any fuel input.
Balance of methane:
The first step is to outline the reactants and products:
𝐶𝐻4 + 𝑎(𝑂2 + 3.76𝑁2 ) → 𝑏𝐶𝑂2 + 𝑑𝐻2 𝑂 + 𝑒𝑁2
It’s worth noting that ambient air is predominantly made up of oxygen and nitrogen. The estimated ratio is
3.76:1 of nitrogen to oxygen. Next, we balance the equation. Ensuring that there is an equal number of
molecules on the reactant and product on each side:
Table 20: Chemical balance for methane
Molecules: Reactants: Products
Carbon =
1
b
Hydrogen =
4
d
Oxygen =
2a
2b + d
Nitrogen = 2(3.76)a
2e
Solving for the molar coefficients:
𝑏=1
𝑑=2
𝑎=
2𝑏 + 𝑑
=2
2
𝑒 = 𝑎(3.76) = 2(3.76) = 7.52
After we have the molar coefficients, we can verify our chemical balance by conducting a mole and mass
balance. The mass balance is achieved by multiplying the mole balance by the molecular weight of each
respective compound.
Molar balance:
1 𝑚𝑜𝑙𝑚𝑒𝑡ℎ𝑎𝑛𝑒 + 9.52 𝑚𝑜𝑙𝑎𝑖𝑟 = 1 𝑚𝑜𝑙𝐶𝑂2 + 2 𝑚𝑜𝑙1 𝑚𝑜𝑙𝐻2 𝑂 + 7.52 𝑚𝑜𝑙𝑁2
10.52 𝑚𝑜𝑙 = 10.52 𝑚𝑜𝑙
Mass balance:
16.04 𝑔𝑚𝑒𝑡ℎ𝑎𝑛𝑒 + 275.6992 𝑔𝑎𝑖𝑟 = 44.01 𝑔𝐶𝑂2 + 36.04 𝑔𝐻2 𝑂 + 211.7632 𝑔𝑁2
291.7392 ≅ 291.8132
Note: mass is off slightly due to precision error of molecular weight.
Table 21 shows the chemical balance for a wet and dry basis. A dry basis is when water is neglected from the
products.
20
Table 21: Wet and Dry basis for methane
Wet Basis:
Dry Basis:
1
1
𝑦𝐶𝑂2 =
= 0.0951 𝑦𝐶𝑂2 =
= 0.117
10.52
8.52
2
𝑦𝐻2 𝑂 = 0
𝑦𝐻2 𝑂 =
= 0.190
10.52
7.52
7.52
𝑦𝑁2 =
= 0.715
𝑦𝑁2 =
= 0.883
10.52
8.52
Sum = 1
Sum = 1.0001 ≅ 1
Using this mass balance, we can now calculate our stoichiometric air to fuel ratio:
𝑚𝑎 = 2(32) + 2(3.76)(28) = 274.56 𝑔𝑎𝑖𝑟
𝑚𝑓 = 1(16.04) = 16.04 𝑔𝑓𝑢𝑒𝑙
𝑚𝑎
274.56
( ) =
= 17.12
𝑚𝑓 𝑠
16.04
With the actual and stoichiometric air to fuel ratio. We can determine our equivalency ratio:
ф=
𝑚𝑓
(𝑚 )
𝑎 𝑎𝑐𝑡𝑢𝑎𝑙
𝑚𝑓
= 0.335
(𝑚 )
𝑎 𝑠
When the equivalency ratio, ф < 1 , that means the engine is running lean.
Image 8: Ranges of equivalency ratio
GREET Analysis:
The natural gas that is used at Cedar Creek is supplied by National Grid (National Grid, 2021). It is
pumped using a natural gas pipeline. The diesel used is supplied by United Energy Corporation (United Energy
Corporation, 2021) gets their petroleum from a refinery in New Jersey called Buckeye Energy Services
(Buckeye Energy Services, 2022). Now having the source of the fuels. We know that they are domestically
sourced. Therefore, when selecting a fuel to use as a model in GREET. We will select one that most closely
meets these criteria.
Natural Gas:
As mentioned previously, the natural gas used at Cedar Creek comes from the northeastern region of the
USA. We know that natural gas is burned in our CIDI engines to produce electricity. Therefore, when selecting
a fuel in the ‘Well to Pump’ tab in the GREET software. We selected ‘NG from Shale and Conventional
Recovery for Electricity Generation’. The corresponding model for this selection can be seen in Image 9.
21
Image 9: Well to Pump process for NG
Additionally, with this model we can generate an emission table for every kJ of energy generated. This table
doesn’t only encompass the emissions of the engine, but all emissions associated with sourcing and then using
the fuel.
Table 22: NG emission per kJ
Emissions:
CO2 Total
5.5069
g
CO2
5.5086
g
CO2_Biogenic -1.72E-06 kg
VOC
8.8612
mg
CO
24.6664
mg
NOx
29.0041
mg
PM10
0.3665
mg
PM2.5
0.346
mg
SOx
10.4743
mg
CH4
0.1743
g
N2O
0.7535
mg
BC
71.0851
ug
POC
0.1452
mg
Diesel:
As mentioned previously, the diesel used at Cedar Creek comes from the northeastern region of the
USA. Specifically, from New Jersey. Therefore, when selecting a fuel in the ‘Well to Pump’ tab in the GREET
software. We selected ‘Conventional Diesel from Crude Oil for US Refineries’. The corresponding model for
this selection can be seen in Image 10.
22
Image 10: Well to Pump process for DSL
Additionally, with this model we can generate an emission table for every kJ of energy generated. This table
only encompasses the emissions associated with sourcing and storing of the fuel.
Table 23: DSL emission per kJ
Emissions:
CO2 Total
12.4943
mg
CO2
12.5142
mg
CO2_Biogenic -1.99E-08 kg
VOC
7.1062
ug
CO
11.7752
ug
NOx
18.0774
ug
PM10
1.2898
ug
PM2.5
1.0842
ug
SOx
4.9432
ug
CH4
0.1059
mg
N2O
0.2313
ug
BC
0.164
ug
POC
0.2948
ug
Emission Comparison:
Having the GREET software allows us to compare the emissions that are associated with sourcing and
using each fuel. The two main pollutants of interest when analyzing an engine are carbon dioxide and nitrogen
oxide. Both of which are inversely related in a CI engine on the tailpipe. In Table 22 and Table 23, we can see
that the process of acquiring natural gas has a much higher level of nitrogen oxide and carbon dioxide relative
to diesel. Seemingly, one would conclude that diesel is better from an emissions perspective. However, the
process for diesel does not include it being used in an engine to generate electricity. So, without the emission
data from the engines, with the emission scope being nitrogen oxide and carbon dioxide. There isn’t a definitive
answer. If the emissions of diesel from the engine, plus the emissions from our model are still less than the
emissions of natural gases. Then making the conclusion that diesel is more efficient from an emissions
perspective is reasonable.
23
Chapter 5:
Conclusion:
When analyzing an engine with different fuels there are many difficulties that arise. More importantly,
it’s even more difficult to conclude concrete findings when there are so many assumptions made when
analyzing the system. Such as, assuming certain fuel properties when moving throughout the cycle,
extrapolating air and fuel usage per cycle via annual purchases, testing all pollutants from the engines not just
required compounds, etc. There are many very simple and easy solutions to implement that would alleviate
many areas of uncertainty. Having volumetric flow meters on the engine to directly read the volume of fuel and
air would make our air to fuel ratio, and by extension our power cycle more accurate. Better yet, implementing
cylinder pressure transducers in tandem with a crankshaft position sensor would directly record instantaneous
data. With said data, we can generate actual instantaneous power cycles for our engines, and not solely rely on
theoretical processes. Additionally, having the fuel properties for our natural gas, diesel, and digester gas would
allow the tailoring of our analysis. For future work, implementing these suggestions would allow for a
comprehensive and accurate analysis.
24
Terminology:
•
ICE – Internal combustion engine
•
CI – Compression ignition
•
SI – Spark Ignition
•
CIDI – Compression ignition direct injection
•
NG – Natural gas
•
DSL -Diesel
References:
Buckeye Energy Services. (2022). Retrieved from https://www.buckeyeenergyservices.com/
Compression Ignition Engine. (2018). Retrieved from https://www.sciencedirect.com/topics/engineering/compressionignitionengine#:~:text=The%20compression%20ignition%20engine%20or,air%20in%20the%20engine%20cylinder.
Diesel Cycle. (2022, June 17). Retrieved from https://en.wikipedia.org/wiki/Diesel_cycle
Diesel Fuel. (2014). Retrieved from Science Direct: https://www.sciencedirect.com/topics/chemistry/dieselfuel#:~:text=(a)%20Diesel%20or%20fuel%20oil&text=It%20consists%20of%20approximately%2075,(e.g.%20ben
zene%2C%20styrene).
Gases - Ratios of Specific Heat. (2003). Retrieved from The Engineering ToolBox:
https://www.engineeringtoolbox.com/specific-heat-ratio-d_608.html
GREET Software. (2022). Retrieved from https://greet.es.anl.gov/
Heywood, J. B. (2000). Internal Combustion Engine Fundamentals. McGraw-Hill.
How Much Energy Does a Wastewater Treatment Plant Use? (2018, March 1). Retrieved from AOS Treatment Solutions:
https://aosts.com/how-much-energy-does-wastewater-treatment-plantuse/#:~:text=Energy%20Star%20reports%20that%20energy,methods%20used%20to%20remove%20them.
Ideal Gas Law. (n.d.). Retrieved from https://en.wikipedia.org/wiki/Ideal_gas_law
National Grid. (2021). Retrieved from https://www.nationalgridus.com/Our-Company/?dest=%2fOur-Company
Sewage Treatment Master Plan. (n.d.). Retrieved from https://www.nassaucountyny.gov/1883/Sewage-TreatmentMaster-Plan
Trapezoid rule. (2022, October 10). Retrieved from https://en.wikipedia.org/wiki/Trapezoidal_rule
United Energy Corporation. (2021). Retrieved from https://www.unrgcorp.com/
Wastewater Digester Energy. (n.d.). Retrieved from https://www.newscientist.com/article/2114761-worlds-first-city-topower-its-water-needs-with-sewageenergy/#:~:text=Carbon%20is%20extracted%20from%20the,to%20make%20heat%20and%20electricity.
25