Abstract
A novel internal combustion-linear generator integrated power system is presented firstly. The system mainly consists of combustion chamber of four stroke internal combustion engine, linear electric generator, reversible electric energy storage system and electronic control unit.
Because the free piston is coupled with movable coil of linear generator, in power stroke electric energy is produced by linear generator. Unlike traditional IC engine there is no crankshaft in the system, so the parameters such as crankshaft speed and angle can not be used to define parameters of linear motion. There are some problems should be solved: 1) how to measure position and speed of the free piston; 2) how to measure indicator diagram; 3) how to measure cycle efficiency of the system; 4)how to measure injector signal and ignition signal.
To solve above 1) a laser optical displacement sensor is proposed. Through measuring displacement of bottom end of the connecting rod position of the free piston can be obtained. Differentiation of displacement is speed of the free piston.
Indicator pressure can be obtained using measuring spark plug with integrated cylinder pressure sensor. Meanwhile together with the laser optical displacement sensor the indicator diagram can be obtained.
In order to measure cycle efficiency of the whole system an intelligent fuel consumption tester is proposed to measure energy input, meanwhile a current sensor and a voltage sensor are proposed to measure electric energy output. Then cycle efficiency can be obtained.
In order to adjust best injection timing and spark timing advance injector signal and ignition signal are measured through communication with ECU.
NI-PXI DAQ card is used to measure above all signals. Using LabVIEW software all signals are acquired, processed, shown and saved.
Until now the whole testing system is set up. Using this testing system some important parameters are acquired, such as TDC, BDC, stroke, motion curve of free piston, speed of the free piston whose desired value is zero at TDC and BDC, indicator pressure, indicator diagram, cycle efficiency which is larger than 32%, injection timing and spark timing advance. These parameters are basis of analysis of performance, parameters adjustment, and control strategy.
Keywords: testing, engine, free piston engine, linear motor, power system