Variable Choked Venturi Brian Gauld, Flamekeeper
WHAT IS THE VcV? A clever device - a short tube with a disk inside The disk floats up and down on a shaft in the center of the tube Normally two VcV s are installed on a stove - one on the primary air inlet and one on the secondary air inlet VcV is a mechanical device - no power is required
HOW IS IT CONNECTED TO THE STOVE? The VcV stove front view Primary VcV is the white object in the centre under the stove, fitted to the primary inlet. (The secondary VcV is fitted to the secondary air inlet behind the primary VcV)
HOW DOES THE P VcV WORK? The disk on the primary VcV will be down when the fire is lit and will stay down until the static pressure reaches a set predetermined amount, enough to sustain a Low burn fire when the P disc pops up As the static pressure increases, the fire draws in more air and this air flow makes the disk pop up As static pressure drops the disk in the P VcV will eventually drop down The primary VcV can be bypassed for high and medium burns by opening the primary air control
THE PRIMARY VcV When the fire is ignited the P VcV disk is at the bottom stop As the fire intensity increases, the static pressure increases, causing the P VcV disk to pop up to the top stop Substantially reduces the amount of primary air entering the stove There are two VcVs normally fitted to a stove The primary VcV (P VcV) is attached to the primary air inlet for the stove Flattened burn curve Reduced dry burn rate Substantially increased overall burn time Increased overall efficiency
HOW DOES THE 2 VcV WORK? The 2 VcV has a funnel shaped bore. When a stove is not in operation or just barely burning, the 2 VcV disc is set to allow a bare minimum of secondary air to enter the stove As the static pressure increases, the disc in the 2 VcV is lifted higher and higher in the bore which allows more and more secondary air to enter the stove. As the fire dies back, the reverse happens. This optimizes the amount of secondary air entering the unit and thus the combustion efficiency (%CE) The 2 VcV operates the same way for all burn rates, again optimizing the amount of secondary air entering the stove and thus the %CE The VcV system is of benefit for all burns, particularly low burn
THE SECONDARY VCV When the fire is ignited the 2 VcV disk is at the minimum setting (bottom stop) As the fire intensity increases, the static pressure increases which causes the 2 VcV disk to rise into the funnel-shaped area in the tube The secondary VcV (2 VcV) is attached to the secondary air inlet for the stove It operates on the same principle as the P VcV, but in reverse Substantially increased amount of secondary air enters the stove Optimized secondary air over entire burn Increased combustion efficiency Increased overall efficiency
The fire is lit OPERATING THE STOVE The primary VcV can be bypassed by opening the primary air control for medium and high burns When operating on medium or high burn, the stove can be switched to low burn by closing the primary air control As the static pressure increases, (1.) the disk in the primary VcV automatically pops up thus reducing the amount of primary air and (2.) the disc in the secondary VcV rises and allows more secondary air to enter the stove. No other adjustments are necessary - on reloading the stove, the VcV s automatically move to correct position
CURRENT ISSUES WITH WOOD STOVES Emissions are too high. Thus EPA is setting new standards Efficiency of stoves also needs improving As a renewable energy source, wood/ biomass has a major role to play in developing energy strategies that help with Climate Change
VcV s - BENEFITS Test results from an EPA accredited laboratory with crib fuel and cord wood show that: Low burn emissions from VcV non cat stoves are well below EPA proposed new Phase 1 requirements (4.5 g/h) and very close to the proposed Phase 2 limit Efficiency for both crib and cord wood increases about 7%. In a VcV controlled non cat stove, low burn overall efficiency (HHV) is increased to over 76% [82% LHV] Fire consumes less fuel, requires less stoking, gives more even heat
SUCCESSFULLY TESTED VcV s are applicable also for boilers and masonry heaters VcV s are visibly and audibly discreet
RESULTS WITH CORDWOOD
RESULTS WITH CRIBWOOD 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Dry Burn Rate (kg/hour) Typical small non-cat stove Stove fitted with VcVs 6 5 4 3 2 1 0 PM Emissions (g/hour) Low performance small non-cat stove High performance small non-cat stove Stove fitted with VcVs 78% 77% 76% 75% 74% 73% 72% 71% 70% 69% Overall Efficiency Typical small non-cat stove Stove fitted with VcVs
RESULTS WITH CRIBWOOD
FOOLPROOF A major cause of increased emissions from wood stoves is Operator Error, where operators close the Primary Air control too soon and the fire does not have enough momentum to sustain itself The P VcV design specifically prevents this happening Even if an Operator closes the primary air control too soon, the primary disc will not pop up until a Low burn fire has built up to where it can sustain itself
PATENTS The VcV has been patented Patents have been issued or the process of examination is being completed, in most countries, outside of tropical areas Patents are in the name of Flamekeeper LLC
OWNERSHIP Flamekeeper LLC is a Florida Registered Company All shares are held by a New Zealand Registered Company, ECO Vision Ltd All shares in the New Zealand Company are owned by the Gauld Family - Directors of Flamekeeper LLC are Alistair Gauld and Brian Gauld Contact Brian Gauld email brian@thevcv.com Ph 0064 9 534 1638 (New Zealand)
DEVELOPMENT All development since 2012 has been carried out in USA, at Colville, WA, at Myren Consulting Inc, an EPA accredited Lab Brian Gauld, New Zealand, is the Team Leader, Eric Schaeffer, WA, Technician Ongoing development to commercial will continue in Colville A stove manufacturer could become involved now as we move to commercial. Initial contact can be made to Brian Gauld or Myren Consulting Inc, Colville, WA
LOOKING AHEAD Low burn is the problem area for many wood stoves. VcV s are the answer. We will seek EPA certification for stoves with VcV s fitted Manufacturers will be able to use VcV s under licence For Manufacturers, licence fees and VcV s will not add a significant amount to stove costs likely to be around US$40 in total
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