LabVIEW is a graphical programming language, also called "G" language, its graphical programming environment has several features that allow the developer to easily create engine test software. LabVIEW programs are called virtual instruments (VIs) because their appearance and operation can imitate actual instruments.
Virtual instruments (VIs) have three main parts: [12]
Front Panel
The front panel simulates the panel of a physical instruments, it can contain knobs, push buttons, graphs, and other controls and indicators. The front panel specifies the user interface of the VI.
Block Diagram
The block diagram consists of the executable code that you create using nodes, terminals and wires, it is a pictorial solution to a programming problem. The block diagram is also the source code for the VI.
Icon and Connector
VIs are hierarchical and modular. You can use them as top-level programs, or as subprograms within other programs. The icon and connector of a VI work like a graphical parameter list so that other VIs can pass data to a sub VI.
With these features. LabVIEW promotes and adheres to the concept of modular programming. You divide an application into a series of tasks, which you can divide again until a complicate application becomes a series of simple subtasks. You build a VI to accomplish each subtask and then combine those VIs on another block diagram to accomplish the larger task. Finally, your top-level VI contains a collection of sub VIs that represents application functions.
3. TPS DEVELOPMENT [5]
In this paper, we used LabVIEW for test program set (TPS) development and for rapidly prototyping user interfaces and program features for immediate operator/customer feedback.
In general, the TPS for an LPG engine consists of a collection of test, each designed to check some aspect of the engine's performance. Each test consists of a series of test steps made up of instructions guiding the operator through manual procedures required for performing that particular test. Mandatory critical engine parameters, as well as operator-selected engine parameters, are monitored and displayed during each test. The operator is given pass/fail and critical parameter alarm (out-of-limits) information during each test, with the option to perform troubleshooting when required. At certain test points, pertinent engine performance data are recorded for incorporation into a final test report, which is printed out after completion of all testing. Fig. 1 is the frame diagram of the LPG engine monitoring system.
4. THE MEASURING DEVICE
The LPG engine configuration is shown in Fig. 2, which includes:
4.1. Main Engine
Our rigs are set up the YANMAR TF120F Diesel Engine, it is one cylinder and four strokes diesel engine, and used the LOVATO's liquefied petroleum gas (LPG). The specifications are listed in Table 1.
4.2. Flow Meter
We used the Teledyne Hastings-Raydist's flow meter (Model HFM-200B). The output signal was sent to Hastings Instruments's Power Supply (Model 400) and amplified to the data acquisition card.
4.3. LPG Fuel System
The advantages of LPG are well mixed with air to reduce air pollution, generally source, stored plentiful and the price is cheap, etc.
4.4. Dynamometer
The dynamometer is coupled with crank-shaft of main engine, the brake power (Pb) can be obtained from equation (1)
Pb= N×Tb, (1)
where N is rpm, Tb is the brake torque (N-m).
4.5. Ignition System
Originally, the engine is operated without sparking plug, and we modify the ignition system.
4.6. Universal Exhaust Gas Oxygen (UEGO) Sensor
There are two sensors of the exhaust gas oxygen (EGO) and the universal exhaust gas oxygen (UEGO) in the discharge tube. The sensor of EGO has a non-linear characteristic, but the UEGO is linear, so we take the UEGO sensor to detect the air/fuel ratio.
4. 7. Encoder
The encoder is coupled with the main engine's cam shaft to convert the shaft angular displacement to rpm. The output was 360 pulse/rpm.
