Event Hosted by Engineers Australia

03/11/2011
 

Norm Mathers - Guest speaker at Annual Event. Event Flyer
 

Improved Safety and Efficiency of Trucks

11/09/2011
 

Article from Queensland Roads 2011 - Improved Safety and Efficiency of Trucks
 

Re-Birth of the Flare Fitting

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Article by Vito Accetta on the Flaretite Fitting
 

Mathers FSV- Fuel Saving Pump Wins the Australian (Queensland) Engineering Awards for Sustainablility

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Fuel Saving Pump Wins the Australian (Queensland) Engineering Sustainablility Award for its Global Potential
 

Mathers Safety Tipper Valve Operation

01/06/2008
 

The Safety Tipper Valve operates in the mining sector
 

Mathers FSV- Fuel Saving Pump

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Hydraulic Technology To Benefit The Transport Sector
 

Discussion on improving cooling efficiency and ambient capability of heavy trucks

16/05/2008

Introduction

The modern heavy truck (GVM > 22.5t), often has its rated power output limited by available engine cooling rather than the design of the engine. The recent introduction of Euro 4 and US 4 emission requirements for vehicles sold in Australia from 2008, has in some cases worsened the problem due to even greater cooling demands. This discussion paper presents a case for using alternative methods of cooling heavy trucks, with benefits such as increased ambient capability, reduced noise and reduced fuel consumption and emissions.

The answer is more power. What was the question?

The automotive industry globally is in constant competition with itself to extract more power from every succeeding model, largely in an attempt to give potential buyers a reason to buy the new model. Sadly more power is not always sourced by greater engine efficiency and often results in both increased fuel consumption and engine cooling requirements.

Design limitations on the cooling capacity of trucks.

Most modern truck engines can be electronically programmed to provide a sizable range of power outputs without any internal mechanical modification. Depending on the intended application, truck design and operating environment, a maximum power output will be specified based on the cooling system’s capacity to maintain a healthy engine operating temperature, not just the maximum power available from a particular engine design. So in hotter climates, a particular truck configuration may not be capable of producing the same power as in a cooler climate. A truck’s ability to operate at maximum power at a specified ambient temperature is known as its ambient capability. Higher ambient air temperatures mean reduced heat transfer from cooling pack to cooling air, and hence reduced cooling capacity which leads to a reduction in available power output since the engine is not able to dispose of its excess heat.

The physical size of a truck cooling pack is most often constrained by the vehicle’s space and packaging limitations. Chassis rails internal width generally restricts the maximum width of the cooling pack since the pack has to fit between them and not in front of them for various other reasons. The height of the cooling pack is controlled from below by the vehicle’s approach angle ground clearance, and from above by driver visibility. For example, a cooling pack positioned low in the chassis, will reduce ground clearance and risk damage, and a cooling pack high in the chassis will force the front corner of the hood higher in a conventional bonneted truck, thus reducing the driver’s frontal visibility. For cab-over trucks internal cab packaging is seriously affected by the height of the cooling pack since it impacts available space on the firewall.

It can be seen that design and layout of the vehicle controls the height and width of the cooling pack, and thermodynamics control the thickness of the cooling pack since heat transfer becomes less efficient for each successive core added to the rear of the cooling pack. Since the amount of heat energy transferred from the cooling pack to the air is proportional to the mass of air passing through it, obviously the faster the truck moves through the air, the greater the cooling capacity. Consequently, a truck moving along at high way speed does not require a great deal of cooling, and at speed above 60km/h the air forced through the cooling pack is sufficient. The problem of insufficient cooling air flow occurs at lower speeds such as pulling a heavy load up a hill. To provide sufficient airflow, all trucks have a belt-driven fan that is engaged by a thermostatically controlled, air-operated clutch.

Belt driven cooling fans as used on trucks are a cheap, reliable and relatively efficient means of pulling air through a cooling pack. Unfortunately, their circular shape contrasted with the rectangular cooling pack means that a very large portion of the cooling pack receives minimal airflow and consequently offers minimal cooling effect, even though shrouds provide some assistance. In addition, belt driven fans are run at a speed proportional to that of the engine and as with most axial flow fans, loose efficiency either side of an optimum rotational speed. Because engine speed may vary anywhere from 800rpm to 1850rpm, the cooling fan may not always be operating in an efficient zone.

These factors lead to two main points.

• Truck power output is often limited by the amount of cooling available.
• Design and packaging requirements dictate a tall rectangular cooling pack which is inefficiently cooled by an engine-driven circular fan.

If a larger area of the cooling pack could receive sufficient airflow, the following three positive outcomes could be achieved:

• The ambient capability of the truck could be increased allowing it to operate in hotter conditions
• The power output could be increased for a set ambient capability
• The size of the cooling pack could be reduced to minimise weight and improve packaging.
• All three of these options could provide a competitive advantage for truck manufacturers.

To achieve greater airflow over the cooling pack area, it follows that more than one fan is required. With a conventional belt driven arrangement, this remains possible, but is likely to become difficult once factors such as belt routing and mounting of the drives to the front of the engine are considered. Electric fans are also a possibility but the power requirement would necessitate overly long and heavy electric motors and wiring due to the relatively low voltage available.

Benefits of using hydraulically driven cooling fans

Hydraulic power may offer a viable solution to this issue for several reasons.