I. Nomenclature
AHRR - Apparent heat release rate
γ
- Ratio of specific heats
P
- Pressure
V
- Volume
θ
- Crank angle
NO
- Nitrogen oxide
NO2 - Nitrogen dioxide
NOx - Nitrogen oxides (NO + NO2)
SOI - Start of injection
SOC - Start of combustion
II. Introduction
Biodiesel is an environmentally friendly alternative to petroleum diesel. It can be
produced from renewable sources generating little carbon dioxide and also often
generates a reduction in exhaust soot emissions. However, it generally increases
emissions of nitrogen oxides (NOx)1. Not only is NOx a significant pollutant, but
tightening emission regulations mean any increase in pollutant levels is concerning.
The objective of this work was to investigate the relationship between various South
Australian produced biodiesel fuels, ignition delay and emissions in a four-stroke,
direct injection, 220cc Yanmar L48AE engine.
There exists a large number of
 Done before by Szybist 2005, Graboski & McCormick, Hribernik & Kegl
(2007, hribernikBDcombustionNemmisionDIengine.pdf), graboski 2002 –
biodiesel source and chemical structure, cardone – performance and emissions
2002, choi & reitz 1999, moshiri 2006- emission and performance effects of
bgiodiesel blends in a sing-cylinder medium-speed diesel engine ( ICES
filename), mccormick 1997 – effect of several oxygenates on regulated
emissions from heavy-duty diesel engines, sharp – exhaust emissions and
performance of diesel engines with biodiesel fuels, wang 2000, Yamane 2001
– influence of physical and chemical properties of biodiesel fuels on injection,
combustion and exhaust emission characteristics in a direct injection
compression ignition engine, zanini – concentration measurement in a road
tunnel
 I applied new Autoignition technique, and more importantly analysed locally
significant/available fuels.
 Should probably have some more background theory here.
III. Experimental apparatus
A Yanmar L48AE engine (properties listed in Table 1) was instrumented with
Table 1: Yanmar L48AE
Type
Cylinders
Displacement
Combustion chamber
1
4-stroke, direction injection, compression
ignition
Single
211cc
Bowl-in-piston design
Graboski, M. Prog. Energy Combust. Sci., 1998; 24:39
Bore X Stroke
70mm X 55mm
Fuel injection
In line pump
Fuel injection pump timing
14±1° BTDC
Fuel injection pressure
19.6MPa
Maximum engine speed (no load)
3800RPM
Maximum output
3.5kW
Cooling
Air
The engine was loaded using a simple magnetic brake and the tangential force from
this magnetic calliper was measured to determine torque output. A burette was gravity
fed from the fuel tank and (by closing a valve in the fuel line) measures the
volumetric fuel consumption.
Cylinder and fuel line pressure was recorded with PCB Piezotronic 112B11 sensors
sampled at 1MS/sec with 12-bit resolution. The data was ensemble averaged over at
least 700 cycles to minimise filtering. A simple Savitsky-Golay filter was
implemented to smooth the data before the pressure trace was differentiated for the
AHRR calculation described below.
Ideal gas and constant specific heat ratio assumptions can introduce errors in diesel
simulations2. Hence an iterative temperature calculation using the thermodynamic
relation (1) was used, with γ calculated from NASA thermodynamic tables3, and gas
composition for dry air from Moran and Shapiro4, with humidity accounted for by a
wet-bulb/dry-bulb measurement performed during data collection.
 1
 P 
Ti  Ti 1  i 
(1)
 Pi 1 
The initial temperature of the cylinder charge was estimated as 330° Kelvin using a
Ricardo WAVE simulation of the engine.
The AHRR is a common calculation which highlights combustion characteristics. As
can be seen in (2)5, it involves the differentials of both pressure and volume. Pressure
was found from the filtered pressure signal, while volume was calculated from engine
geometry and a crank angle sensor signal, with a resolution of 2000 points per cycle.

dV
1
dP
(2)
AHRR 
P

V
  1 d   1 d
Ignition delay is defined as the time between the start of injection (SOI) and the start
of combustion (SOC)5. Opening pressure of the injector was determined as 20.0MPa
by using a poppet valve tester. The SOI was defined as when pressure in the fuel line
(measured as close as was practical to the injector) exceeded 20.0MPa. Using the
high-pressure speed of sound measurements by Tat6, the maximum delay between the
pressure wave reaching the transducer and the injector opening was approximately
0.02ms, and was considered negligible.
SOC was originally determined using the first moment of positive heat release,
however this criterion was changed to the maximum of the third differential of
2
Musculus, M. SAE Special Publication SP-1974, 2005
Smith, G.P. et al. http://www.me.berkeley.edu/gri_mech
4
Moran, M.J. and Shapiro, H.N. Fundamentals of Engineering Thermodynamics, Jon Wiley & Sons
Inc., New York; 1999
5
Heywood, J.B. Internal Combustion Engine Fundamentals, McGraw Hill Inc., Singapore; 1988
6
Tat, M.E. Investigation of oxides of nitrogen emissions from biodiesel-fueled engines, Ph.D. Thesis,
Iowa State University, Iowa; 2003
3
pressure (as recommended by Katrasnik7) for a more repeatable SOC measurement.
Emissions (O2, CO, NO, NO2, and unburnt hydrocarbons) were monitored using a
Testo 350 XL gas analyser sampling at the muffler’s exit. Particulate matter was
measured with a MAHA DPMS 04 particulate measurement system, which uses a
laser light scattering photometer.
The accuracy of each variable reported is shown in Table 2.
7
Katrašnik, T. et al.J. Eng. Gas Turbines and Power 128 (1); 2006
Table 2: Accuracies
Measurement
NO, NO2, CO
Oxygen
Particulate matter
SOI, SOC
Ignition delay
Temperature
Pressure
Accuracy
±5% of measurement value
±0.8% concentration
±1mg/m3
±2° crank angle
±0.01ms
±30°K
±5kPa