The current PROMETS and PROGEN models

Each of the variants of PROMETS mentioned previously (Gasoline, Diesel, Inline, V-type) and be run in either single, or multi-cylinder mode. In single cylinder mode, the state of each cylinder is assumed to be identical and the coolant in the head and in the block is considered a uniform mass. When multi-cylinder mode is run, differences in boundary conditions for each of the individual cylinders and the coolant path through the engine are considered; the inboard cylinders are said to be adiabatically connected on both sides while the outboard cylinders have outer surfaces that are connected to ambient conditions.

The version of PROMETS referred to in the rest of this work will be the single cylinder representation of an inline 4 cylinder spark ignition engine, and the corresponding version of PROGEN. In this section, the model is described in the form before revisions were made as part of the project.

The PROMETS model itself consists of 7 subsections which represent important systems of the engine. There are the Cylinder and Port Heat Flux, Frictional Losses, Coolant Heat Transfer, Oil Heat Transfer, Exhaust Gas Temperature, Fuel Flow Prediction, and Structure Heat Transfer. These subsections are explored in the coming sections.

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The 4 cylinder gasoline version of PROGEN generates a representation of the engine consisting of 41 lumped capacity elements of varying physical and thermal properties, depending on the specified materials and design constraints. Element sizes vary throughout the model: areas of greater complexity, or those expected to experience greater thermal gradients, such as the valve and intake/exhaust ports require higher resolution, and therefore smaller element sizes. Areas which are not heavily involved in thermodynamic process or are relatively remote, such as the crankcase walls are represented by fewer, larger elements. The element positions and their numbering are shown in Figures 3.1 to 3.3. Scaling factors are included which can be used to improve the accuracy of predicted element and fluid volumes and masses. They allow adjustment of PROGEN predictions of characteristics such as wall thicknesses in the coolant jacket, cylinders and crankcase, coolant volume in the head, block and auxiliaries and thickness of the piston ring pack. There are 10 scaling factors used in the current version of PROGEN. The scaling factors are not required to be altered before PROGEN runs, and are instead used to refine the results of the lumped capacity generator.

The variables listed in Tables 3.1 and 3.2 are the dimensions and options that need to be specified in order for PROGEN to generate the lumped capacity engine representation. These variables have been physically measured during a tear down of the VIPER engine. In addition to the physical characteristics of the engine, the model must also be supplied with details of the desired operating conditions of the test that is to be simulated. Inputs that are required by the model are engine speed and load. Other conditions such as the fuel flow rate, heater matrix flow rate, AFR, or exhaust temperature can either be predicted within the model, or dictated to the model if specific metrics for these values are required. The workflow for running a simulation is as follows. PROGEN must first be run; this populates a MATLAB workspace with the dimensions and properties of the elements which make up the engine representation. Next, a set of operating conditions must be input to the model to define the desired test. Once this information is received, the PROMETS model can be run.

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Figure 3.1 PROMETS block element positions

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Figure 3.2 PROMETS cylinder head element positions

Figure 3.3 PROMETS valve element positions

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Table 3.2. Head Variables for PROGEN

PROMETS name Description Notes

A2IN Intake port vertical dimension B2IN Intake port horizontal dimension

FIN Distance between head gasket and intake port bottom

IN_VALVE_DIA Intake valve diameter -1=unknown

EX_PORT_LENGTH Exhaust port length

A2EX Exhaust port vertical dimension B2EX Exhaust port horizontal dimension

FEX Distance between head gasket and exhaust port exit bottom

EX_VALVE_DIA Exhaust valve diameter -1=unknown

VALVE_ANGLE Valve included angle MAX_VALVE_LIFT Maximum valve lift

NUM_IN_VALVE Number of intake valves per cylinder NUM_EX_VALVE Number of exhaust valves per cylinder

VT_CONFIG Valve train configuration 1= Single Overhead Cam with Finger Follower 2= Single Overhead Cam with Rocker Arm

3= Direct Acting Single Overhead Cam

4= Direct Acting Double Overhead Cam

5= Overhead Valve

FOLLOWER_TYPE Follower type 1= Flat Follower

2= Roller Follower

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Table 3.1. Block Variables for PROGEN

PROMETS name Description Notes

BORE Cylinder bore

STROKE Engine stroke NUM_CYL Number of cylinders

WALL_TH1 Total wall thickness surrounding cylinder

COOL_LEN Mean Coolant passage height ^{Of the coolant jacket} surrounding the cylinders

COOL_TH Mean Coolant passage width See above

BORE_SPACE Distance between Bore centres

LINER_TH Liner thickness -1 for no liner

HEAD_WIDTH Head width

-1 for unknown. Mean distance between intake and exhaust manifold decks.

LINER_MAT Liner material 1=Aluminium alloy, 2= Cast

iron

HEAD_MAT Head material 1=Aluminium alloy, 2= Cast

iron

BLK_MAT Block material 1=Aluminium alloy, 2= Cast

iron

PTN_MAT Piston material 1=Aluminium alloy, 2= Cast

iron

PISTON_DEPTH Piston depth

CON_ROD Connecting rod length Distance between the bearings RING1TOP Distance from piston crown to top of 1st ring

PACK_HGT Ring Pack height

DELTAC Distance between inside and outside edge of ring Mean of the 3 rings

RING_THK Piston ring thickness Mean of the 3 rings

RINGS_K Piston ring thermal conductivity NUM_BEARINGS Number of bearings

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