A vehicle gasifier is the same downdraft (Imbert) design as a stationary one, built smaller, welded and made to survive vibration, and sized by its throat diameter to the engine it feeds: 60-75 mm for a 1.0-1.5 litre engine up to 100-130 mm for 2.5-4.0 litres. The unit alone weighs about 125-235 kg before the 50-80 kg of fuel is loaded, so it suits trucks and vans better than small cars.
Part of Wood Gas Vehicles
Vehicle gasifier design covers sizing to the engine, the weight and space it takes, and the materials that survive heat, vibration and tar.
What Changes From A Stationary Unit
The principle is unchanged: fuel moves down, air enters at a throat, and the gas passes through the hot bed (Downdraft (Imbert) Gasifier). Three things change on a vehicle:
- The load swings. An engine going from idle to a hill changes its gas demand many times over, and a throat sized for one rate runs cold and tarry at low load.
- The unit must be compact. Everything has to ride on a chassis.
- Everything shakes. Vibration cracks joints and loosens bolts, and a gas leak in a moving vehicle is lethal.
Sizing And The Parts, From The Carrier
| Engine size | Throat diameter | Firetube diameter | Wood use |
|---|---|---|---|
| 1.0-1.5 L | 60-75 mm | 200-250 mm | 15-25 kg per 100 km |
| 1.5-2.5 L | 75-100 mm | 250-300 mm | 25-40 kg per 100 km |
| 2.5-4.0 L | 100-130 mm | 300-400 mm | 40-60 kg per 100 km |
The throat is again one third of the firetube. The sizing is examined in Downdraft Gasifier Sizing for Vehicles, and the consumption column is worked in Range & Fuel Consumption.
Weights from the carrier:
- Reactor 50-100 kg, cyclone 15-25, cooler 20-40, filter 10-20, piping, frame and hopper 30-50.
- Sum of the parts: 125-235 kg.
- With 50-80 kg of fuel: 175-315 kg. The carrier states the total as 150-300 kg “including” the fuel; its own parts sum to different totals at both ends, so plan on its list, not its total. See Weight & Space Constraints.
What You Need
- The engine’s displacement and the duty (small car, van, truck), to pick the size row.
- A mounting plan before the design is final (Vehicle Mounting).
- A cleaning train that fits (Gas Cleaning for Mobile Use).
- Materials for heat and vibration (Material Selection for Mobile Use).
Common Mistakes
- Oversizing the throat for hills. Idle and cruise then run cold and tarry. A bigger throat helps only the peak.
- Copying a stationary build. It lacks vibration isolation and compact cleaning.
- Forgetting the performance penalty. A converted engine makes 40-60% of rated power (Power Output Derating).
Safety
Carbon monoxide travels with the vehicle
Producer gas is about 18-22% carbon monoxide by volume, and a vehicle puts the gas line beside the cab, the engine bay and the operator. Never run, light or warm up the gasifier in a garage, shed, lean-to or enclosed yard, even briefly, and never sleep in or near a vehicle with a lit unit. Every joint on a gas line is a leak path under vibration. Start-up gas is cool, rich and almost entirely carbon monoxide. See Carbon Monoxide Risks.
What’s Next
- Learn next: Downdraft Gasifier Sizing for Vehicles — checking the table against the engine
- Combine with: Building a Downdraft Gasifier — the build, before the vehicle changes