Engine Testing and Control Dynamometers Fuel and Air Measurement Exhaust Gas Measurement and Analysis In-Cylinder Pressure Measurement Engine Sensors and Actuators Engine Control Dynamometers Hydraulic – Water Break • Absorption only • Rotor moves through a fluid, viscous dissipation absorbs energy Eddy Current • Current induced as magnets move through coils • Current passes through resistors which heat up and provide resistance to the motion of the electrons • Absorption only Motoring AC or DC Dynamometer • Current induced by magnets rotating through coils • Current can be applied to coils to rotate the motor and the attached engine – motoring • Current produced can be pushed against existing voltage making a generator, placing power in the grid or into a battery Dynamometers Water Brake Dynamometers Dynamometers Eddy Current Dynamometer Dynamometers AC Motoring Dynamometer Fuel Flow Measurement Measurement is complicated by return flow Gravimetric Scale • May use a load cell or visual reading Pressure and orifice • Calibrate the flow through a hole as a function of pressure difference Turbine flow meter • Volume flow rate of fuel is proportional to turbine speed (our gasoline engine) • Density of the fuel must be known, requires separate temperature measurement and conversion Coriolis • Flow through a vibrating U-Tube produces a twisting moment proportional to mass flow rate. (Diesel Engine) Air Flow Measurement Choked flow orifice • As long as the flow remains choked (P1/P2 > 2), the flow is proportional to the upstream pressure • Limited flow range Calibrated Orifice • Flow is determined from up and downstream pressure and temperature Turbine Flow Meter • Volume flow rate is proportional to turbine speed • Density must be determined (separate pressure and temperature measurement) Hot Wire Anemometer • Current heats a wire that changes resistance as air flow cools the wire. Air Flow Measurement Choked flow orifice Calibrated flow orifice Turbine Flow Meter Hot Wire Anemometer Exhaust Gas Measurement Zirconia Oxide O2 – Sensor Sensor Creates a voltage difference related to O2 partial pressure 0.2 – 0.8 V O2 CO2 O2 CO2 CO2 O2 O2 CO2 O2 Air, Reference O2 N2 Zirconia Membrane Exhaust Side O2 CO2 N2 O2 N2 N2 O2 O2 Platinum Electrodes Gas Permeable N2 N2 Exhaust Gas Measurement CO2 – CO – Both use Non Dispersive Infrared (NDIR) Absorption Exhaust Gas Measurement Hydrocarbons Uses A Flame Ionization Detector (FID) Ions are proportional to the concentration times the number of carbon atoms per molecule. For Example: If calibrated with 100 ppm CH4 then 100 ppm of propane C3H8 will produce 300 ppm on the readout Exhaust Gas Measurement NOx – Uses Chemiluminescence Analyzer NO reacts with O3 (Ozone) to produce N2O which then gives off a photon. NO O 3 NO *2 O 2 NO *2 NO 2 photon NO *2 M NO 2 M Exhaust Gas Measurement O2 – Uses Polarographic Analyzer Membrane allows the diffusion of O2 proportional to the concentration O2 O2 O2 O2 O2 KCl O2 O2 O2 O2 O2 O2 O 2 O2 O2 O2 Analyzers use consumable sensors which will require replacement after a period of time. O2 O2 2 H 2O 4e 4OH O2 O2 Gold, Au Silver, Ag Silver, Ag 4 Ag 4Cl 4 AgCl 4e O2 O2 Net flow of electrons from anode to cathode Exhaust Gas Measurement Zirconia Oxide O2 – Sensor Sensor Creates a voltage difference related to O2 partial pressure 0.2 – 0.8 V O2 CO2 O2 CO2 CO2 O2 O2 CO2 O2 Air, Reference O2 N2 Zirconia Membrane Exhaust Side O2 CO2 N2 O2 N2 N2 O2 O2 Platinum Electrodes Gas Permeable N2 N2 In-Cylinder Pressure Measurement Quartz Piezoelectric Detector Optical Encoder Calculating Heat Release From Cylinder Pressure Using the Energy Equation, Ideal Gas Law and Constant Specific Heats dU Qin Qout dV P dt dt dt dt d cons * dt Qin Cv P dV CvV dP Qout P d R d d R d PV mRT Qin PC p dV CvV dP Qout C C d C C d d d v p v p PC p PCv dV C vV dP Qout Qin Cv P Qin dU dV Qout mC v d T dV Qout P P d d C C C C R d d v p v p d d d d d d d dT dV dP dT P dV V dP P V or d d d d mR d mR d Qin V dP dV Qout P dV mC v P d d d mR d mR d mR Qin Cv P dV CvV dP dV Qout P d R d R d d d Qin 1 dV 1 / dP Qout P V d 1 1 / d 1 1 / d d Qin dV 1 dP Qout P V d 1 d 1 d d This result says we can measure the heat added per crank angle by measuring the rate of pressure rise and the rate of volume change. PC p PCv dV C vV dP Qout Qin Cv P d C C d d R C C d v p v p Calculating Heat Release From Cylinder Pressure CvV dP Qout Qin PC p dV C C d C C d d d v p v p Using the Energy Equation, Ideal Gas Law and Constant Specific Qin 1 dV 1 / dP Qout V P Heats d 1 1 / d 1 1 / d d Qin dV 1 dP Qout V P d d 1 d 1 d Pressure (psi) Pressure (kPa) 13.33788 91.9614454 13.59174 93.71174849 13.59174 93.71174849 13.8456 95.46205158 13.8456 95.46205158 14.09946 97.21235466 14.09946 97.21235466 14.09946 97.21235466 14.60718 100.7129608 14.35332 98.96265775 14.60718 100.7129608 14.86104 102.4632639 Work (kJ) P_smooth Q-Dot Q_dot_s 0 5.7543E-07 2.29891E-06 5.22402E-06 9.31847E-06 1.46786E-05 2.12293E-05 2.89703E-05 3.82229E-05 4.85258E-05 6.02433E-05 7.34177E-05 95.80357 96.65738 97.42581 98.23692 99.2188 100.1153 101.1399 102.2071 0.001093 9.17E-05 0.000108 0.002174 -0.00088 0.00119 0.001213 0.000571 0.000539 0.000583 0.000701 0.000671 0.000765 0.000811 Calculating Heat Release From Cylinder Pressure The apparent heat release and a smoothed once and smoothed twice results are shown Calculating Equivalence Ratio From Exhaust Gas The mixture fraction, xf The fuel air ratio in terms of mixture fraction The equivalence Ratio Engine Sensors Oxygen Sensor – Narrow and Wide Band Crank Position Engine Speed Throttle Position Manifold and Ambient Pressure Inlet Air and Coolant Temperature Intake Air Flow Knock Actuators
